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Abstract

A bench-top physical model eye that closely replicates both anatomical and optical properties of an average human eye was designed and constructed. The cornea was sourced from a flouro-polymer with refractive index (RI) of 1.376 and crystalline lenses were made of Boston RGP polymers, EO and Equalens II, with an equivalent RI of 1.429 and 1.423 respectively. These materials served to make crystalline lens components of different age groups and accommodative states. De-Ionized water, with RI of 1.334 represented both aqueous and vitreous humor. The complementary metal-oxide sensor of a PixelLink digital camera with a resolution of 5MP and a 2.2µm pixel pitch, hosted on a motor-base, served as the ‘acting’ retina. The translation and rotary functions of the motor-base facilitated the simulation of different states of ametropia and assessment of peripheral visual function, respectively. We validated one of its configurations to suit normal viewing conditions and results from the on and off-axis optical quality measurements are presented. As a demonstration of potential practical uses, several corrective soft contact lenses were placed on the model eye and their optical performance evaluated.

Figures (8)

A simplified mechanical layout of the developed physical model eye presented with three test channels. Channel 1 includes a moveable visual display unit. Channel 2 consists of optical bench set-up for single-pass measurements. The light is first attenuated with neutral density filter (ND), further spatially filtered using a microscopic objective (SF) (8mm EFL), and 50µm pinhole; and collimated with achromatic doublet L1 (250mm EFL). Channel 3 is used for double-pass measurements via COAS aberrometer. A relay system consisting L2 and L3, 125mm EFL each, is used to increase the working distance of aberrometer.

A snapshot of the constructed physical model eye. A magnified overview of the anterior chamber of the model eye shows the humidity chamber, cornea and sclera. The individual elements including cornea and crystalline lens are also shown in highlighted subsection.

Through-focus point spread functions captured at the retinal plane by photoactive sensor and their respective radially averaged modulation transfer functions of one subset configuration of the model eye (unaccommodated 25 year old), at 4 mm pupil diameter.

Point spread functions of the 25-year old unaccommodated model eye configuration captured in the ‘virtual’ retinal space (imaged by photoactive sensor) for retinal eccentricities from 0° to 30°, at 5mm pupil diameter.